Conventionally, sensors are used widely for analyzing biogenic substances such as glucose, cholesterol, etc. For instance, a glucose sensor is used for the self-control of a diabetic's blood-sugar level. Generally, the glucose sensor is an electrode sensor in which a working electrode and a reference electrode are formed on a substrate, and reagents such as glucose oxidase and potassium ferricyanide are provided thereon. When this electrode sensor is placed in a measuring device and a diabetic puts his blood collected by himself onto the reagent part, the glucose oxidase oxidizes the glucose contained in the blood to cause electrons to be transferred and thereby the current value changes. The change in current value then is detected with the pair of electrodes and is measured with the measuring device to be converted into the blood-sugar level, which then is displayed. The potassium ferricyanide mediates the transfer of electrons caused through an oxidation-reduction reaction and thus is referred to as a mediator. This substance delivers electrons to and receives electrons from the electrodes. This transfer of electrons that occurs between the electrodes and the mediator is carried out at high speed, which results in a higher measuring speed. The sensor is stored in a container as one of a plurality of sensors and is taken out when it is used.
The container for the sensors, however, is not transparent and therefore the number of sensors cannot be checked visually from the outside. Accordingly, in order to check the number of sensors visually, it is necessary to open the container, which is inconvenient. In addition, the sensors are exposed to the outside air every time the number of sensors is checked visually, and this causes the sensors to deteriorate due to oxidization caused by or humidity brought by the air, which has been a problem.